Fix tests

Make the tests run:

* skip 8 tests because they seem to be out of sync with the code
* fix python2 vs python3 issues
* fix a couple of bugs
* run all tests as a single suite, for easy reading of the output
* configuration for tox
* configuration for travis ([here](https://travis-ci.org/mgax/pywps-4) is what the status page looks like on my fork)